Ideally, you want to move the p-trap so it is directly underneath the new pan's hole. TO do this, you may need to crack some more concrete to gain access. Depending on which way it drains and the direction you need to move it, the height may differ, but it's almost imperceptible at 1/4 of a foot and 1/4"/foot (or 1/16"). Assuming the existing trap is in good condition, a coupler and a short stub of pvc is all it would take. Maybe a shallow angle of an elbow, depending on the direction of the pipe, or probably easiest to get the position just right, is a new p-trap since you can glue it up at an angle and would have more flexibility in location.